The use of near-infrared interferometry allowed the team to resolve a ring-shaped dust distribution (generally called "dust torus") in the inner region of the nucleus of the active galaxy NGC 3783. This method is able to achieve an angular resolution equivalent to the resolution of a telescope with a diameter of 130 Meters. The resolved dust torus probably represents the reservoir of gaseous and dusty material that "feeds" the hot gas disk ("accretion disk") and the supermassive black hole in the center of this galaxy.
Artist's view of a dust torus surrounding the accretion disk and the central black hole in active galactic nuclei. Credit: NASA E/PO - Sonoma State University, Aurore Simonnet (http://epo.sonoma.edu/)
The Very Large Telescope Interferometer of the European Southern Observatory. Photo: Gerd Weigelt/MPIfR
Extreme physical processes occur in the innermost regions of galactic nuclei. Supermassive black holes were discovered in many galaxies. The masses of these black holes are often a millionfold larger than the mass of our sun. These central black holes are surrounded by hot and bright gaseous disks, called "accretion disks". The emitted radiation from these accretion disks is probably generated by infalling material. To maintain the high luminosity of the accretion disk, fresh material has to be permanently supplied. The dust tori (see Fig. 1) surrounding the accretion disks are most likely the reservoir of the material that flows through the accretion disk and finally "feeds" the growing black hole.
Observations of these dust tori are very challenging since their sizes are very small. A giant telescope with a mirror diameter of more than 100 Meters would be able to provide the required angular resolution, but unfortunately telescopes of this size will not be available in the near future. This raises the question: Is there an alternative approach that provides the high resolution required?
The solution is to simultaneously combine ("interfere") the light from two or more telescopes since these multi-telescope images, which are called interferograms, contain high-resolution information. In the reported NGC 3783 observations, the AMBER interferometry instrument was used to combine the infrared light from two or three telescopes of ESO's Very Large Telescope Interferometer (VLTI, see Fig. 2). This interferometric method is able to achieve an extreme angular resolution that is proportional to the distance between the telescopes. Since the largest distance between the four telescopes of the VLTI is 130 Meters, an angular resolution is obtained that is as high as the theoretical resolution of a telescope with a mirror diameter of 130 Meters - a resolution that is 15 times higher than the resolution of one of the VLTI telescopes, which have a mirror diameter of 8 Meters.
"The ESO VLTI provides us with a unique opportunity to improve our understanding of active galactic nuclei,", says Gerd Weigelt from the Max-Planck-Institut für Radioastronomie in Bonn. "It allows us to study fascinating physical processes with unprecedented resolution over a wide range of infrared wavelengths. This is needed to derive physical properties of these sources."
And Makoto Kishimoto emphasizes: "We hope to obtain more detailed information in the next few years by additional observations at shorter wavelengths, with longer baselines, and with higher spectral resolution. Most importantly, in a few years, two further interferometric VLTI instruments will be available, which can provide complementary information."
To resolve the nucleus of the active galaxy NGC 3783, the research team recorded thousands of two- and three-telescope interferograms with the VLTI. The telescope distances were in the range of 45 to 114 Meters. The evaluation of these interferograms allowed the team to derive the radius of the compact dust torus in NGC 3783. A very small angular torus radius of 0.74 milli-arcsecond was measured, which corresponds to a radius of 0.52 light years. These near-infrared radius measurements, together with previously obtained mid-infrared measurements, allowed the team to derive important physical parameters of the torus of NGC 3783.
"The high resolution of the VLTI is also important for studying many other types of astrophysical key objects", underlines Karl-Heinz Hofmann. "It is clear that infrared interferometry will revolutionize infrared astronomy in a similar way as radio interferometry has revolutionized radio astronomy."
The research team comprises scientists from the Universities of Florence, Grenoble, Nice, Santa Barbara, and from the MPI für Radioastronomie.
Contact:Prof. Dr. Gerd Weigelt,
Norbert Junkes | Max-Planck-Institut
Beyond the brim, Sombrero Galaxy's halo suggests turbulent past
21.02.2020 | NASA/Goddard Space Flight Center
10,000 times faster calculations of many-body quantum dynamics possible
21.02.2020 | Christian-Albrechts-Universität zu Kiel
The operational speed of semiconductors in various electronic and optoelectronic devices is limited to several gigahertz (a billion oscillations per second). This constrains the upper limit of the operational speed of computing. Now researchers from the Max Planck Institute for the Structure and Dynamics of Matter in Hamburg, Germany, and the Indian Institute of Technology in Bombay have explained how these processes can be sped up through the use of light waves and defected solid materials.
Light waves perform several hundred trillion oscillations per second. Hence, it is natural to envision employing light oscillations to drive the electronic...
Most natural and artificial surfaces are rough: metals and even glasses that appear smooth to the naked eye can look like jagged mountain ranges under the microscope. There is currently no uniform theory about the origin of this roughness despite it being observed on all scales, from the atomic to the tectonic. Scientists suspect that the rough surface is formed by irreversible plastic deformation that occurs in many processes of mechanical machining of components such as milling.
Prof. Dr. Lars Pastewka from the Simulation group at the Department of Microsystems Engineering at the University of Freiburg and his team have simulated such...
Investigation of the temperature dependence of the skyrmion Hall effect reveals further insights into possible new data storage devices
The joint research project of Johannes Gutenberg University Mainz (JGU) and the Massachusetts Institute of Technology (MIT) that had previously demonstrated...
Researchers at Chalmers University of Technology, Sweden, recently completed a 5-year research project looking at how to make fibre optic communications systems more energy efficient. Among their proposals are smart, error-correcting data chip circuits, which they refined to be 10 times less energy consumptive. The project has yielded several scientific articles, in publications including Nature Communications.
Streaming films and music, scrolling through social media, and using cloud-based storage services are everyday activities now.
After helping develop a new approach for organic synthesis -- carbon-hydrogen functionalization -- scientists at Emory University are now showing how this approach may apply to drug discovery. Nature Catalysis published their most recent work -- a streamlined process for making a three-dimensional scaffold of keen interest to the pharmaceutical industry.
"Our tools open up whole new chemical space for potential drug targets," says Huw Davies, Emory professor of organic chemistry and senior author of the paper.
12.02.2020 | Event News
16.01.2020 | Event News
15.01.2020 | Event News
21.02.2020 | Medical Engineering
21.02.2020 | Health and Medicine
21.02.2020 | Physics and Astronomy